Due to the asymmetric design of the disk body as well as due to the forces resulting from the solution, its mounting on the bearing journal must be designed such that both radial and axial forces can be transmitted. These forces are relatively high because of the principle of action of disk bits during use in solid rocks. Since the forces to be applied decrease considerably with the reduction in the diameter of the disk bit, mining equipment that is equipped with disk bits having smaller, compact disk bodies can be used either in even harder rock or with a smaller amount of energy applied and with a more favorable wear behavior.
In mining machines such as surface miners with a mining mechanism rotatable around its horizontal axis, the material separated by the tools is delivered, in general, by threads from the outside to the inside toward the middle of the mining mechanism, where it is transferred onto a removing conveyor. The tools are arranged over the entire width of the mining mechanism in the lines of these threads at a certain distance from each other. The space between the jacket of the mining mechanism, the threads with the tools and the face (wall) is available as the transportation space for the separated material. If flat or round-shaft bits are used as the tools, they can be integrated within the threads because of their compact size. By contrast, the transverse conveying of the separated material would be substantially limited due to the bulky design in the case of equipping with conventional disk bits. To reach an economical mining output, the disk bit should have a free radial wedge height (the free radial wedge height corresponds to the dimension from the external hub diameter of the disk body to the cutting circle of the mining mechanism and is also called penetration capacity) of up to ¼ of the disk diameter with maximum rigidity. A disk bit intended for use in the mining mechanism of a surface miner must therefore be designed as a slender and robust mini disk bit.
Disk bits are successfully used in tunneling and in mining for removing or mining solid rocks. A crushing and at the same time splitting effect is achieved in the solid rock during the rolling of the disk bit on the solid rock with its wedge-shaped disk body. Strong pressing forces, which act on the tool as axial and radial forces, are necessary for this. The disk bits must consequently have a correspondingly robust design. This applies to both their dimensions and the shape, the selection of the material and the quenching and tempering as well as the mounting. While the design of these tools is solved in the case of disk bits in which the diameter of the disk body is 300 mm or greater, mounts of special designs must be provided in the case of smaller tools with asymmetric design of the disk body, because commercially available bearings are too large.
For example, a small disk bit with a disk body of asymmetrical cross section, in which the axis is supported on both sides at a fastening web and a slide bearing is provided between this axis and the disk body, is known from the article “Kontinuierlicher Gewinnungsvmechanismg im Festgestein” [Continuous Mining in Solid Rocks] published in the journal Surface Mining—Braunkohle & Other Minerals, Vol. 53 (2001), No. 2, pp. 185-190, FIG. 2, drawing on the right-hand side. The slide bearing comprises a bush, which is provided with front ring disks on both sides. The bush is split vertically in the center, so that a two-part slide bearing is formed. The radial forces are transmitted via the two halves of the bush to the fastening webs of the disk bit. Due to the splitting of the slide bearing, there is no clearance laterally in the area of the ring disks under radial load. The use of the slide bearing makes it possible to design the disk bit as a compact disk bit. However, two-sided support is associated with a great width. The sealing problems are not solved satisfactorily, either.
Even more slender designs can be obtained with an overhangingly arranged disk bit, as is known from the reference book “Mechanical Mining of Hard Ores Occurring in Layers of Small Thickness in Underground Mining” (original title: MEKHANIZI[R]OVANNAIA PODZEMNAIA RAZRABOTKA KREPKIKH RUD MALOMOSHCHNYKH MESTOROZHDENII), Chita (Russia), 1999, p. 130. This prior art is shown in FIG. 1. The bit holder B is fastened to the rotating tool holder A of a mining device. This bit holder B is provided with a conical hole C for accommodating the truncated cone-shaped bearing journal D. The bearing journal D has a cylindrical track E for a cylindrical roller bearing F, which assumes the task of a radial bearing. A ball groove G for a ball bearing H is milled into the circumference of the circle between the cylindrical track E and the truncated cone of the bearing journal D. This ball bearing H is a thrust bearing and a radial bearing at the same time. The disk body comprises three parts: The outer cutting ring I and the inner, two-part carrying and also ball bearing disk J and K. These three components are connected to one another by bolts L. The disk body is supported on the bearing journal D by means of a combined antifriction bearing, comprising a cylindrical roller bearing F and a ball bearing H. The inner track E for the cylindrical roller bearing F and the inner ball groove G for the ball bearing H are, as was described above, integrated in the overhanging part of the bearing journal D. The outer track M for the cylindrical roller bearing F and the outer ball groove N for the ball bearing H are located, by contrast, in the hole of the inner two-part carrying and also ball bearing disk J and K. The inner space of this combined antifriction bearing is closed to the outside by a cover O. To reduce the width of the bit, the disk body is supported according to this design only by a row of cylindrical rollers and an adjacent row of balls. This design of the disk bit and the bearing journal D offers the advantage that the diameter and the width of the disk body are relatively small.
Since the smallest possible width of the disk bit is desirable for the overhanging design, the width of the disk body is still considerable with two antifriction bearings F and H arranged next to each other. The manufacture of the multipart disk body I, J and K and of the entire disk bit also requires a great effort and causes high costs. At the same time, the multipart disk body guarantees a limited rigidity only. The rigidity of the bolted-together bit body also decreases with the reduction of its diameter.
Furthermore, a cutting or picking roller equipped with disk and round-shaft or flat bits for coal-mining equipment, in which the disk and round-shaft or flat bits are arranged one behind another in the direction of cutting in the threads, is known from DE 34 42 875 C2. In order to prevent the conveying of the separated material between the threads by the protruding disk bits with its holders from being compromised due to jamming, two annular side walls are additionally arranged in parallel to one another in the threads on the jacket of the picking roller and covered by a steel strip. The side walls and the steel strip are interrupted and thus they permit the disk bits to be accommodated on the jacket of the picking roller in the gaps of the threads. The disk bits integrated within the threads with their holders are thus protected and cannot hinder the material transport. The round-shaft or flat bits are fastened to the strip steel.